Remote aromatic stabilization in radical reactions

Cabellero, Alfonso Garcia; Croft, Anna K.; Nalli, Stefano M.

doi:10.1016/j.tetlet.2008.04.009

Cited by 10 publications

(10 citation statements)

References 25 publications

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“…[76] An analogous effect of a through-space π-interaction on reactivity has been seen in rigid models, whereby the aromatic ring is fixed in position with respect to the incipient radical centre. [77] Relative rates of radical reduction were found to be larger for anthracene-based derivatives with electron-withdrawing aromatic substituents than for those with electron-rich rings, in line with the expectation for a relatively electron-rich transition state ( Fig. 6).…”

Section: Partial Protonationsupporting

confidence: 83%

Radicals by Design

Croft¹,

Lindsay²,

Renaud³

et al. 2008

Chimia

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Radical reactions offer many advantages over conventional chemical reactions, lending themselves to numerous bond forming processes and rearrangements that are, clean, rapid, and tolerant of a wide range of functional groups. This review provides a brief overview of the design concepts behind new reactions illustrating, in particular, their relevance for the efficient synthesis of biomolecules. Tw o general reactions are highlighted: single electron transfer (SET) using SmI 2 and hydrogen transfer using reagents such as those based on tin, thiols and phosphorous reagents. Intermolecular influences that may direct radical reactions, such as partial protonation and radical complexation, are also discussed.

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Section: Partial Protonationsupporting

confidence: 83%

Radicals by Design

Croft¹,

Lindsay²,

Renaud³

et al. 2008

Chimia

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“…124,125 Anion-arene interactions have also been invoked to explain the rates of free radical halogen-abstraction reactions in a series of anthracene derivatives, 1-phenyl-4-bromodecane and a non-aromatic control molecule. 126 DFT calculations and experimentally measured reaction rates suggest that the presence of an aromatic ring in these systems stabilizes the electron-rich transition state. Nearly an 8-fold increase in reaction rate is observed for a nitro-substituted anthracene derivative over a nearly isostructural methyl derivative.…”

Section: Supporting Solution Evidence For Anion-arene Interactionsmentioning

confidence: 93%

Experimental evidence for interactions between anions and electron-deficient aromatic rings

2009

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This feature article summarizes our research aimed at using electron-deficient aromatic rings to bind anions in the context of complementary research in this active field. Particular attention is paid to the different types of interactions exhibited between anions and electron-deficient arenes in solution. The 120+ references cited in this article underscore the flurry of recent activity by numerous researchers in this field, which was relatively nascent when our efforts began in 2005. While the interaction of anions with electron-deficient aromatic rings has recently garnered much attention by supramolecular chemists, the observation of these interactions is not a recent discovery. Therefore, we begin with a historical perspective on early examples of anions interacting with electron-deficient arenes. An introduction to recent (and not so recent) computational investigations concerning anions and electron-deficient aromatic rings as well as a brief structural survey of crystalline examples of this interaction are provided. Finally, the limited solution-based observations of anions interacting with electron-deficient aromatic rings are summarized to introduce our current investigations in this area. We highlight three different systems from our lab where anion-arene interactions have been investigated. First, we show that tandem hydrogen bonds and anion-arene interactions augment halide binding in solution. Second, a crystallographic and computational study highlights the multiple types of interactions possible between anions and electron-deficient arenes. Third, we summarize the first example of a class of designed receptors that emphasize the different types of anion-arene interactions possible in solution.

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“…The synthesis of 1 was achieved in two steps by adapting previous procedures described in the literature (Scheme S1). , Benzoquinone (3.25 g, 30 mmol), isoprene (10.0 mL), and traces of hydroquinone (two spatula tips), were suspended in 20.0 mL of absolute ethanol. The mixture was placed in a 40.0 mL autoclave and heated at 130 °C for 6 h. Once the autoclave reached room temperature, the mixture was dissolved in a potassium hydroxide solution in ethanol (8.5 g of KOH in 200 mL of EtOH) in a round-bottom flask.…”

Section: Methodsmentioning

confidence: 99%

Proton-Coupled Electron Transport in Anthraquinone-Based Zirconium Metal–Organic Frameworks

et al. 2017

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The ditopic ligands 2,6-dicarboxy-9,10-anthraquinone and 1,4-dicarboxy-9,10-anthraquinone were used to synthesize two new UiO-type metal-organic frameworks (MOFs; namely, 2,6-Zr-AQ-MOF and 1,4-Zr-AQ-MOF, respectively). The Pourbaix diagrams (E vs pH) of the MOFs and their ligands were constructed using cyclic voltammetry in aqueous buffered media. The MOFs exhibit chemical stability and undergo diverse electrochemical processes, where the number of electrons and protons transferred was tailored in a Nernstian manner by the pH of the media. Both the 2,6-Zr-AQ-MOF and its ligand reveal a similar electrochemical pK value (7.56 and 7.35, respectively) for the transition between a two-electron, two-proton transfer (at pH < pK) and a two-electron, one-proton transfer (at pH > pK). In contrast, the position of the quinone moiety with respect to the zirconium node, the effect of hydrogen bonding, and the amount of defects in 1,4-Zr-AQ-MOF lead to the transition from a two-electron, three-proton transfer to a two-electron, one-proton transfer. The pK of this framework (5.18) is analogous to one of the three electrochemical pK values displayed by its ligand (3.91, 5.46, and 8.80), which also showed intramolecular hydrogen bonding. The ability of the MOFs to tailor discrete numbers of protons and electrons suggests their application as charge carriers in electronic devices.

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Remote aromatic stabilization in radical reactions

Cited by 10 publications

References 25 publications

Radicals by Design

Radicals by Design

Experimental evidence for interactions between anions and electron-deficient aromatic rings

Proton-Coupled Electron Transport in Anthraquinone-Based Zirconium Metal–Organic Frameworks

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